Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal malignancies. The median survival for patients with advanced PDA is 6 months and 5-year survival rate is <5%. One of main reasons for such poor prognosis is the extreme treatment resistance of PDA. One major mechanism for that resistance is thought to be the low rate of drug penetration into the tumor bed, caused by the high intratumor interstitial fluid pressure (IFP) as a result of the stromal desmoplasia in PDA. The dense stromal matrix in PDA is a result of the overproduction of extracellular matrix (ECM) proteins such as collagens, hyaluronan, and SPARC (secreted protein acidic and rich in cysteine). Our team has been exploring different approaches to target these ECM components to reduce stromal stiffness and improve drug uptake. So far we have had some very encouraging results. Based on our prior work documenting that stromal SPARC is increased in tumors taken directly from patients we performed a Phase I/II clinical study of the combination of the albumin-bound (nab)-paclitaxel targeting SPARC added to gemcitabine. That regimen has given a documented disease control rate of 68% (CR + PR + stable for >16 weeks) in patients with stage IV disease with some complete remission. The median survival of patients with stage IV PDA was 12.2 months. The patients' response correlated very well with the level of SPARC in their tumor stroma but not in tumor cells. Most recently, to attack a second stromal component (hyaluronan) we performed a Phase I clinical trial with the pegylated human recombinant hyaluronidase (PEGPH20). Previously bovine hyaluronidase was shown to improve drug perfusion and efficacy in both animal models and pilot clinical trials. However, further clinica development was hampered by the immunological response to the bovine enzyme. Results from our Phase I study demonstrated a good safety profile and promising activity for PEGPH20. We are working on additional clinical trials of nab-paclitaxel + gemcitabine with or without PEGPH20. Based on the above promising results of targeting tumor stroma, in this application we propose to target collagen, the major component of ECM matrix. Our hypothesis is that reducing stromal collagen will result in stromal collapse in PDA which will in turn decrease IFP and enhance the penetration of chemotherapeutics into tumor tissues and consequently improve drug efficacy and patient survival. We seek to test this hypothesis by performing preclinical studies proposed in the following specific aims: Aim 1: to investigate the effect of pancreatic stellate cell (PSC) inactivation either by Rho kinase (ROCK) inhibitors or by halofuginone to disrupt collagen dynamics and improve drug perfusion and uptake in PDA; Aim 2: to investigate the ability of agents that inhibit collagen synthesis/secretion to improve tumor perfusion and uptake of chemotherapeutic agents in PDA; Aim 3: to evaluate the efficacy of combination treatment of a collagen targeted agent plus gemcitabine or gemcitabine + nab-paclitaxel or other clinically promising regimens both against patient primary xenografts developed by our team and the KPC mouse model for PDA.